Articulated Mobile Robot Research Articles

Semiautonomous recovery system from a stuck state of an articulated mobile robot

ABSTRACT A semiautonomous system is presented in this paper that recovers an articulated mobile robot from a stuck state in which the robot cannot move forward due to contact with the environment. Assuming the specific robot, the stuck states are classified into four types, depending on the position of contact with the environment. In the recovery system, the contact area causing the movement failure is identified using a contact position and magnitude of contact force obtained by the pressure sensor mounted on the robot. Motion candidates for recovery from each stuck state are autonomously calculated and presented to the operator via the user interface. The operator then selects an appropriate motion from the candidates, and the robot performs the recovery motion. An articulated mobile robot with sensors was developed, and experiments were conducted to demonstrate the effectiveness of the proposed system. As a result, the recovery of the robot from each stuck state using the proposed system was verified.

Kinematic modeling and motion characterization of an articulated mobile robot

In response to the outstanding problems of poor motion flexibility and poor terrain adaptability of conventional mobile robots in unstructured environments, a multi-vehicle modular articulated mobile robot capable of adapting to complex and variable obstacle terrain was developed by designing and introducing a flexible articulation device. By constructing a kinematic model of the single body module of the robot, integrating the motion constraint relations among the modules, and establishing the overall robot attitude equations, we propose a robot soft motion control method. Based on the analysis of robot motion characteristics under special obstacle terrain, the relationship model between obstacle parameters and robot pose is constructed, and the correction strategy under unilateral unstable motion state is proposed through the analysis of robot motion state under unilateral unstable condition. Theoretical analysis and experimental results show that the robot has good motion flexibility and complex terrain adaptability.

Development of an articulated mobile robot moving on magnetic curved walls and passing over obstacles

We developed an articulated mobile robot that can move on the magnetic curved walls and traverse through obstacles for wall surface inspections of a large tank. This robot is equipped with magnetic wheels and is able to stick to and move on steel wall. We add passive roll joints and turn off the torque of the pitch joints to ensure the wheels keep in contact with the curved surface. The developed robot is tested through experiments in the laboratory and also in a field test at the World Robot Summit 2020. The experiments are conducted to confirm the movements of the robot on the curved wall surface and when the units are lifted for obstacle traversal. As the results, the robot is not able to overcome an obstacle near the wall such as a handrail but is able to move freely on the curved wall surface and traverse some obstacles on the corner.

Development and control of an articulated mobile robot T2 snake-4.2 for plant disaster prevention – development of M2 arm and C-hand

ABSTRACT In this study, we develop an articulated mobile robot T Snake-4.2 that can move in narrow spaces, climb stairs, gather information, and operate valves for plant disaster prevention. We developed a novel folding arm M2 arm, fitted to the articulated mobile robot to have a better performance in mobility and operation ability compare to previous work T Snake-4. We introduce a novel method of climbing high steps and stairs by using the M2 arm as a support for the articulated mobile robot. T Snake-4.2 can climb high steps and stairs even with a heavy folding arm. In addition, we present a novel valve operating end effector, C-hand which allows the articulated mobile robot to open a large valve. By utilizing the shape characteristic of the valve, C-hand constraints to the environment and rotates the valve handle without transferring any reaction force to the robot and the folding arm. The developed robot T Snake-4.2 is tested through experiments in the laboratory and also in a field test at the Plant Disaster Prevention Challenge of World Robot Summit 2020.

Local body shape control of an articulated mobile robot and an application for recovery from a stuck state

This paper proposes a method for an articulated mobile robot to change its local body shape in a complex environment. By coexisting a heuristic approach which is easy to design a motion in a complex three-dimensional environment and a model-based approach which can utilize the redundancy of the robot, the robot achieves propulsion in a complex environment and the local body shape control simultaneously. A part of the robot's body shape is changed based on a kinematic model, whereas the rest of it is controlled to follow the original shape or maintain its original position based on a heuristic method. As an application of the proposed method, the recovery motion from a stuck state is proposed. The robot is recovered from a stuck state by controlling the part of the robot that is in collision with an obstacle to move it away from the obstacle. The effectiveness of the proposed method is verified by experiments on an actual robot.

Development of an Articulated Mobile Robot Moving on Magnetic Curved Walls

Development of an Articulated Mobile Robot Moving on Magnetic Curved Walls

Three-dimensional steering for an articulated mobile robot with prismatic joints with consideration of hardware limitations

ABSTRACT The paper presents a three-dimensional steering method for an articulated mobile robot that contains links, rotational joints, prismatic joints, and active wheels. The robot can change the angles of its links using the rotational joints and vary the lengths of its links using the prismatic joints. The target motion of this robot is represented by a continuous curve and the motions of the joints and the wheels are calculated by fitting the entire robot to this target curve. The forward velocity of the robot's head is adjusted to satisfy the hardware limitations of the robot; e.g. joint angle, joint velocity, and wheel velocity limitations. In addition, a terrain-following method is presented that considers the changes in the lengths of the links. An experimental articulated mobile robot was developed and experiments were carried out to demonstrate the effectiveness of the proposed method.

Development of a folding arm on an articulated mobile robot for plant disaster prevention

In this work, we develop a folding arm on an articulated mobile robot to inspect an industrial plant. The design targets of the arm, its operations, measurement ability, and mobility, were set for the task of inspecting an industrial plant. To accomplish the targets, we designed the folding arm considering both accessibility to high locations and the mobility of the articulated mobile robot to which it is attached. The arm has links, joints, dummy wheels, and sensors and enables the robot to which it is attached to manipulate objects, e.g. rotating valves, opening a door, or inspecting by accessing high locations. In addition, changing the posture of the arm and touching the dummy wheel in the arm to the surrounding terrain can reduce any negative effect of the arm on the robot's mobility when it encounters narrow spaces, stairs, steps, and trenches. The arm is controlled as a six degrees-of-freedom manipulator without redundancy by an operator who directly sets two joint angles. The effectiveness of the developed arm was demonstrated not only through experiments in a laboratory but also in a field test at the Plant Disaster Prevention Challenge of the World Robot Summit 2018.

Development and field test of the articulated mobile robot T2 Snake-4 for plant disaster prevention

In this work, we develop an articulated mobile robot that can move in narrow spaces, climb stairs, gather information, and operate valves for plant disaster prevention. The robot can adopt a tall position using a folding arm and gather information using sensors mounted on the arm. In addition, this paper presents a stair climbing method using a single backward wave. This method enables the robot to climb stairs that have a short tread. The developed robot system is tested in a field test at the World Robot Summit 2018, and the lessons learned in the field test are discussed.

Task-Space Control of Articulated Mobile Robots With a Soft Gripper for Operations

A task-space method is presented for the control of a head-raising articulated mobile robot, allowing the trajectory tracking of a tip of a gripper located on the head of the robot in various operations, e.g., picking up an object and rotating a valve. If the robot cannot continue moving because it reaches a joint angle limit, the robot moves away from the joint limit and changes posture by switching the allocation of lifted/grounded wheels. An articulated mobile robot with a gripper that can grasp objects using jamming transition was developed, and experiments were conducted to demonstrate the effectiveness of the proposed controller in operations.

System Locally Changing Form of Articulated Mobile Robot

System Locally Changing Form of Articulated Mobile Robot

Development and Control of Articulated Mobile Robot for Climbing Steep Stairs

In this paper, we develop an articulated mobile robot that can climb stairs, and also move in narrow spaces and on 3-D terrain. This paper presents two control methods for this robot. The first is a 3-D steering method that is used to adapt the robot to the surrounding terrain. In this method, the robot relaxes its joints, allowing it to adapt to the terrain using its own weight, and then, resumes its motion employing the follow-the-leader method. The second control method is the semi-autonomous stair climbing method. In this method, the robot connects with the treads of the stairs using a body called a connecting part, and then shifts the connecting part from its head to its tail. The robot then uses the sensor information to shift the connecting part with appropriate timing. The robot can climb stairs using this method even if the stairs are steep, and the sizes of the riser and the tread of the stairs are unknown. Experiments are performed to demonstrate the effectiveness of the proposed methods and the developed robot.

Hierarchical Fuzzy Control System for a Mobile Robot Angular Orientation. Part I

The paper presents the existing algorithms and ways of passing labyrinths. Hardware and software were developed for an automated control system of a mobile robot angular orientation in labyrinths. The paper describes the elements included into the robot, as well as a scheme of their linking-up. One of the factors, which limit the use of the robotic systems in industry, is a small memory size of the microcontrollers. In order to compensate for this shortage, a fuzzy algorithm of passing based on analysis of the incoming information from the sensors was presented. In order to process the information coming from the sensors an articulated mobile robot control concept is used, based on a hierarchical fuzzy synthesized MISO-system. Its distinguishing feature is that the parameters of the previous level of the output are the input to the next level. A concept is presented for processing information coming from the sensors of the mobile robot control. It is based on a hierarchical fuzzy synthesized MISO-system. They make the system additive, and ensure its higher levels of accuracy and functionality. They make the system additive, and ensure higher levels for accurate events. Assessment of accuracy is carried out by the standard deviation (RMSE). The best system has a minimal value of RMSE. The experimental modeling presented in the paper confirms the adequacy of the developed fuzzy system.

Smooth control of an articulated mobile robot with switching constraints

The paper describes a smooth controller of an articulated mobile robot with switching constraints. The use of switching constraints associated with grounded/lifted wheels is an effective method of controlling various motions; e.g. the avoidance of a moving obstacle. A model of an articulated mobile robot that has active and passive wheels and active joints with switching constraints is derived. A controller that accomplishes the trajectory tracking of the robot’s head and subtasks using smooth joint input is proposed on the basis of the model. Simulations and experiments are presented to show the effectiveness of the proposed controller.

Singularity Analysis of a Snake Robot and an Articulated Mobile Robot With Unconstrained Links

In this paper, we analyze the conditions related to singular configurations with unconstrained links and present related theorems and lemmas for a snake robot and an articulated mobile robot. A snake robot and an articulated mobile robot have links that have passive or active wheels and the links are serially connected by active joints. The singular configuration should be avoided if the robots are automatically controlled because they cannot execute intended motion when they are in the singular configuration. We derive a novel necessary and sufficient condition for the singular configurations of the snake robot; this removes some limitations of the traditional condition for a snake robot without unconstrained links. We also derive the necessary and sufficient conditions for the singular configurations of the articulated mobile robot, and the structural conditions under which a real articulated mobile robot does not have a singular configuration. These conditions are proved by analyzing the elements of matrices included in the kinematic model and considering the geometrical meaning of the elements. In addition, we propose evaluation indices representing the distance from the singular configurations of a snake robot. We verify the effectiveness of these indices through simulations.

能動車輪型多連結ロボットの開発と手動環境適応推進

This paper presents an articulated mobile robot for urban search-and-rescue. The robot has active wheeled links connected by active joints, and is designed to move on various environments, e.g., plane, stairs, and narrow spaces. Moreover, this paper presents a method for three-dimensional locomotion which accomplishes that the body shape of an articulated mobile robot adapts to environment using its own weight. The adaptation to environment is obtained manually by making the joints passive. The experimental result demonstrates the effectiveness of a proposed method.

多連結移動ロボットのためのタフな通信システムの開発

This paper presents a tough communication system for an articulated mobile robot. The system which consists of many micro-computers can communicate servo motors via serial communications, gather sensor information, and detect errors of both communications and servo motors. Moreover, it decreases communication time between the robot and the computer for controlling the robot, and keeps operating without stopping even if communication error in micro-computers and actuators occurs.

多連結清掃ロボットの開発と机上清掃制御

多連結清掃ロボットの開発と机上清掃制御

1P2-R07 狭所・段差の清掃が可能な多連結掃除ロボットの開発と制御

In this paper, we develop an articulated mobile robot for cleaning on steps and narrow paths. The robot consists of links which has a cleaning unit, wheels for propulsion, a pitch joint for three-dimensional motion, and sensors for collision detection, and the links are serially connected by a yaw joint. A control method which the robot effectively cleans a plane floor is proposed, and simulations and experiments were carried out to demonstrate the effectiveness of it. Furthermore, experiments were performed to test feasibility of climbing a step.

Analysis of Articulated Mobile Robots for the Urban Search and Rescue

Articulated structure of mobile robot presents high flexibility on the environment adaptation. It has been widely used on the mobile robot to get through rough terrain. This class of robots named as articulated mobile robots can move in hard condition with high stability and environment adaptability. In order to satisfy the requirement of Urban Search and Rescue (USAR), a series of articulated mobile robots are analyzed. The performance of articulated mobile robots is analyzed for get an appropriate robot for USAR. Two snake-like robots named Perambulator I and II are analyzed. Based on the structure of Perambulator II, the articulated mobile robot Ameba II are presented based on track drive mechanism. Ameba II has high performance on mobility and adaptability in complex environment. The comparisons among of some typical articulated robots are given based on mobility and environment adaptation. The experimental results of both Perambulator II and Ameba II show that the Ameba II mobile robot is a better than the snake-like robot Perambulator II on the urban search and rescue applications.